The present invention relates to an assembly of a rim for mounting a tire and an annular run-flat support intended for mounting on the rim. This assembly is particularly useful for extending the distance a tire may travel at reduced or even zero air pressure. In particular, the present invention relates to a run-flat support having a particular arrangement of the reinforcement elements in the radially inner portion of the run-flat support. Many solutions have been proposed for providing an annular run-flat support fixed to a wheel rim to allow extending running after a partial or total loss of air pressure—capability for extended mobility. Many of these systems include multi-piece rims or multi-piece supports and their use necessitates a complicated and time-consuming assembly process.
To overcome some of this difficulty, U.S. Pat. No. 5,891,279 describes an assembly comprising a tire, a rim having a unique profile designed to accept the tire, and a deformable, but preferably circumferentially inextensible, run-flat support ring that is slipped over an essentially cylindrical bearing surface of the rim. The base of the support ring includes essentially inextensible, circumferentially oriented reinforcement elements to resist the centrifugal forces generated by highway-speed travel. The support ring may be designed with an interference fit between the support and the bearing surface of the rim. When mounted, this interference causes a pretension in the reinforcement elements in the base of the support to resist better the centrifugal forces. The support is fixed in position laterally on one end by an axial protuberance and on the other end by one of the tire beads. The support also functions to prevent unseating of one of the bead seats in the event of a loss of inflation pressure in the tire. This type of run-flat assembly has an enormous advantage in ease of assembly and in extended mobility distance of travel when compared to many of the rigid, multi-piece supports. However, this invention can incur a penalty in excess mass for the support.
As an improvement having the possibility to reduce the mass of the run-flat support, International Application WO 01/08905 describes an assembly of a rim and an annular support element where each bead seat of the rim is capable of preventing unseating of the beads in the event of a loss of pressure without the aid of the run-flat support. Since the support no longer functions to retain one of the bead seats, this feature of the rim allows the width of the support to be “clipped” or reduced in width to reduce the mass of the support. Lateral location of the support is accomplished by a stop projecting axially from the rim that acts against one end of the support, and by an axial protuberance projecting from the radially inner face of the support that interlocks with a similarly shaped recess in the bearing surface of the rim.
As an alternative to the improvement just described, U.S. Pat. application Publication US2003/0005991 describes a similar rim and run-flat support assembly with a plurality of zones having protuberances on the bearing surface of the support but without the complementary depression in the rim. Each of these zones has a secondary circumferential reinforcement that is uncoupled from the primary circumferential reinforcement by a circumferential void that allows circumferential extension of the two reinforcements.
However, these inventions must accept a compromise in the level of lateral locating force developed when the run-flat support is mounted on the rim. This force must be sufficiently low to allow proper seating of the support during the assembly process and to allow ease of disassembly should a repair be necessary. During extended mobility operation of the assembly, the force must also be sufficiently high so that the support maintains its lateral position when the assembly is subject to lateral forces between the inside of the tire and the support, such as those that arise when the vehicle negotiates a curve. If the locating force is insufficient, the support may move laterally and result in a reduction of handling performance under extended mobility operating conditions. Even when these designs develop an acceptable lateral locating force, experience has shown that the tensile stresses in the reinforcement elements may be unevenly distributed, especially in the zone immediately outward of the locating protuberance.